Michael is $4$ times as old as Brandon and is also $27$ years older than Brandon. How old is Michael?
Solution: We can use the given information to write down two equations that describe the ages of Michael and Brandon. Let Michael's current age be $m$ and Brandon's current age be $b$. ${m = 4b}$ ${m = b + 27}$ Now we have two independent equations, and we can solve for our two unknowns. One way to solve for $m$ is to solve the second equation for $b$ and substitute that value into the first equation. Solving our second equation for $b$, we get: ${b = m - 27}$. Substituting this into our first equation, we get the equation: ${m = 4}{(m - 27)}$ which combines the information about $m$ from both of our original equations. Simplifying the right side of this equation, we get: $m = 4m - 108$. Solving for $m$, we get: $3 m = 108$. $m = 36$.